Graduate Thesis Or Dissertation
 

Ethanolysis products from bark flavonoids and polymeric phenolics

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  • Ethanolysis reactions were conducted on the flavonoids, such as, catechin, quercetin and dihydroquercetin, and polymeric phenolic components from conifer barks, such as, mountain hemlock phlobatannin and Douglas-fir phlobaphene with the object of ascertaining their chemical relationship. These reactions were carried out with absolute ethanol in the presence of 2.5% hydrogen chloride at the boiling temperature with and without the presence of zinc dust. Identified ethanolysis products from dihydroquercetin were eriodictyol, quercetin and luteolin. When zinc dust was added to the reaction mixture, the products were eriodictyol and phloroglucinol. Ethanolysis of dl-catechin gave pyrocatechol, 2, 4, 6-trihydroxyacetophenone and phloroglucinol. Similarly, in the presence of zinc dust this compound gave protocatechuic acid and phloroglucinol. Quercetin gave protocatechuic acid and 2, 4, 6-trihydroxybenzoic acid, and in the presence of zinc dust protocatechuic acid and phloroglucinol. When it was treated in aqueous ethanolysis solution with zinc dust, quercetin gave protocatechuic acid and its esterified product, ethyl protocatechuate. Ethanolysis of mountain hemlock phlobatannin gave pyrocatechol, protocatechuic acid and phloroglucinol. In the presence of zinc dust the ethanolysis products were d-catechin, 1-epicatechin and phloroglucinol. The results suggest that mountain hemlock phlobatannin is a polymer of dl-catechin. Douglas-fir phlobaphene gave protocatechuic acid, ethyl protocatechuate and dihydroquercetin, and in the presence of zinc dust dihydroquercetin. The results suggest that dihydroquercetin is linked in some way to Douglas-fir phlobaphene by either an ester or ether linkage, From this research, ethanolysis and its modified process with zinc dust were found to assist in the understanding of the fundamental structure and chemical relationship between the flavonoids, phlobatannins and phlobaphenes.
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